This surely is an exciting and very important field of
inquiry for those people interested in social dynamics among group members
and the factors that make individuals change their behavior when they
observe others performing certain acts.

Seeing is feeling: Monkey see, monkey feel, monkey do

A recent essay by Michael Marshall in New Scientist magazine called "Monkeys
chill out just from seeing their friends being groomed" caught my eye. It's
only available to subscribers, but the original research article by Juliette
Berthier and Stuart Semple about which Mr. Marshall is writing titled
"Observing grooming promotes affiliation in Barbary macaques" is available
for free and is a relatively easy read. These scientists write, "Observing
friendly social interactions makes people feel good and, as a result, then
act in an affiliative way towards others. Positive visual contagion of this
kind is common in humans, but whether it occurs in non-human animals is
unknown. We explored the impact on female Barbary macaques [Macaca silvanus]
of observing grooming, a behaviour that physiological and behavioural
studies indicate has a relaxing effect on the animals involved."

To learn more about the presence of positive visual contagion in these
monkeys, 20 individually identified semi-free-ranging adult females
comprising 154 pairs were observed at Trentham Monkey Forest
(Stoke-on-Trent, UK). The researchers were specifically interested in
testing the hypothesis that observing grooming leads to positive contagion.
They note, "Such contagion could result in positive changes in affective
state, promote grooming, increase rates of other affiliative behaviour, or
inhibit agonistic behaviour; we explored predictions related to each of
these four possibilities." (See note [1] below for more details about their
predictions.)

Female macaques display positive visual contagion

The researchers found the first example of positive visual contagion in
nonhumans. They report, "seeing conspecifics groom was associated with a
reduction in a behavioural indicator of anxiety among bystanders, suggesting
that seeing others groom is, in itself, relaxing. In addition observation of
grooming bouts was associated with increases in a range of affiliative
behaviours, including grooming itself. These findings provide evidence from
a non-human species that observing affiliative interactions of conspecifics
can lead to positive contagion. This work further highlights the importance
of exploring animal social behaviour not just at the level of the
interacting individuals, but also within the broader social environment in
which the behaviour occurs." It's also interesting to ponder the possible
role of mirror neurons when various motional states are shared among members
of a social group.

Emotional contagion among dogs at play: Go to the dogs and take a
bow

I look forward to more studies like this on other nonhuman primates and
nonhumans representing different taxa. It would be surprising to learn that
positive visual contagion is limited to these monkeys or only to other
nonhuman primates, but we really don't know. It's a perfect example of a
phenomenon that's been observed by other researchers and non-researchers
among different animals. For example, in our long-term field study of wild
coyotes we often remarked about how play was "socially contagious." And,
having observed many 1000s of play bouts in domestic dogs, other canids
(members of the dog family), and other nonhumans, I've seen what could be
called positive visual contagion on countless occasions, and many people
have reported this phenomenon as well. In fact, there's an empirical study
on dogs by Elisabetta Palagi, Velia Nicotra, and Giada Cordoni that
demonstrates this phenomenon, but it was not called "positive visual
contagion." (See "Rapid mimicry and emotional contagion in domestic dogs,"
"Dog Play Is Socially Contagious and Now We Know Why" for a summary of Dr.
Palagi's study), Canine Confidential: Why Dogs Do What They Do, and "The
Power of Play: Dogs Just Want to Have Fun.")

Among dogs and other animals, an action called the play bow is very
important in initiating and maintain the "play mood," and in a summary of
the above study by Jennifer Viegas (no longer available online) we read,
"The researchers documented that in less than one second, many of the dogs
would copy the expressions and behaviors of other dogs. For example, if one
dog would position his body in a play bow, indicating readiness to play,
another would do so near instantaneously. If a dog exhibited a relaxed,
open-mouthed face — signifying friend not foe among canines — then the other
dog would tend to do the same."

When I was asked to comment on the study by Dr. Palagi and her colleagues, I
wrote that this is a very important study because not only does it extend
the taxonomic distribution of rapid mimicry and emotional contagion to a
species in which they have been inferred but not adequately demonstrated,
but also because it explains a wealth of data showing that dogs (and other
animals) can engage in high intensity social play and "fine-tune it on the
run." During decades of detailed research on dog play by my students and I,
we hypothesized that dogs were somehow empathizing with their play partners
and that this was one of the reasons that even high intensity play only
rarely escalated to "true aggression," but we hadn't invoked mimicry as one
reason they could vigorously play and share intentions to play and maintain
the play atmosphere. Now, Dr. Palagi and her colleagues have shown that the
ability to maintain a "play mood" most likely rests on rapid mimicry and
emotional contagion

One interesting aspect of Dr. Palagi's study is that "the distribution of
rapid mimicry was strongly affected by the familiarity linking the subjects
involved: the stronger the social bonding, the higher the level of rapid
mimicry." Along these lines, a study in progress shows that play among dogs
who are familiar does indeed differ from play among dogs who haven't
previously played. We've also noticed that play in large groups of dogs
breaks down more rapidly than play in smaller groups, not because it
escalates into aggression but rather, we argue, that the dogs can't read one
another as well in large groups. This remains an on-going study so please
stay tuned for more information on this aspect of social play in dogs.

Where to from here?

"Overall, the findings of this study further highlight the importance of
moving the analysis of animal social behaviour beyond the level of the
interacting individuals, to take into account the broader social
environment; in doing so, we feel there are a number of key avenues for
future exploration."

Stay tuned for more discussion of the possible bases for sharing good
feelings among group members without having to actually partake in a social
interaction. There still is much to learn. For example, Berthier and Semple
conclude, "Finally, it would be valuable to explore interspecific variation
in this phenomenon to test, for example, whether propensity to positive
contagion covaries with species’ social style (e.g. tolerant/despotic).
Studies of these kinds are needed if we are to appreciate the role that
positive visual contagion plays in the life of social animals." I totally
agree. This surely is an exciting and very important field of inquiry for
those people interested in social dynamics among group members and the
factors that make individuals change their behavior when they observe others
performing certain acts.

We predicted firstly that the observation of grooming would reduce
bystanders’ rates of self-directed behaviour (prediction 1). We also
predicted that observing grooming would reduce the time to bystanders' next
grooming bout (prediction 2a), that levels of visual attention while
observing grooming would be negatively related to the time to the next
grooming bout (prediction 2b), and that observing grooming would increase
the likelihood both of bystanders initiating grooming (prediction 2c) and of
them being the groomer rather than groomee (prediction 2d). We predicted
that observing grooming would increase bystanders’ rates of approaching
other individuals (prediction 3a), the proportion of time they spent in
close proximity to others (prediction 3b) and their rates of (non-grooming)
affiliative behaviour (prediction 3c), but would reduce their rates of
aggressive behaviour (prediction 4)."

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